Neuropsychological characteristics of Huntington's disease carriers: a double blind study

Semantic clustering on common list-learning tasks: a systematic review of the state of the literature and recommendations for future directions

INTRODUCTION

On some list-learning tasks, such as the California Verbal Learning Test (CVLT) or Hopkins Verbal Learning Test (HVLT), examinees have the opportunity to group words based on semantically related categories (i.e., semantic clustering). Semantic clustering (SC) is often considered the most efficient organizational strategy and adopting SC is presumed to improve learning and memory. In addition, SC is conceptualized as reflecting higher-order executive functioning skills. Although SC measures have intuitive appeal, to date, there are no comprehensive reviews of the SC literature base that summarize its psychometric utility. In this systematic review, we synthesize the literature to judge the validity of SC scores.

METHOD

We conducted a systematic literature search for empirical articles reporting SC from the CVLT and HVLT. We qualitatively described the relationship of SC with other list-learning and cognitive test scores and clinical diagnoses, contrasting SC with serial clustering and total learning scores when possible.

RESULTS

SC was inversely correlated with serial clustering. Higher SC was strongly associated with better learning and memory performances. When compared with cognitive tests, SC tended to have the strongest relationships with other memory measures and modest relationships with tests of executive functioning. SC had negligible to small relationships with most other cognitive domains. Traditional memory scores yielded stronger relationships to cognitive test performances than did SC. SC across clinical groups varied widely, but clinical groups tended to use SC less often than healthy comparison groups.

CONCLUSION

Our comprehensive review of the literature revealed that SC is strongly related to measures of learning and memory on the CVLT and HVLT and is correlated with a wide range of cognitive functions. SC has been understudied in relevant populations and additional research is needed to test the degree to which it adds incremental validity beyond traditional measures of learning and memory.

Mindfulness-Based Stress Reduction in Pre-symptomatic Genetic Frontotemporal Dementia: A Pilot Study

Pre-symptomatic frontotemporal dementia (FTD) mutation carriers and first-degree family members that are 50% at-risk for FTD may experience symptoms of anxiety and depression as a result of the ambiguity of when or if symptoms of the disease will manifest. We conducted a pilot study to investigate the use of an online mindfulness-based stress reduction (MBSR) course to reduce symptoms of anxiety and depression in presymptomatic frontotemporal dementia (FTD) mutation carriers and individuals 50% at-risk. Seven known mutation carriers and six individuals 50% at-risk completed a standardized 8-week MBSR course, and filled out pre- and post and two-month follow-up questionnaires. The primary outcome measure was the Hospital Anxiety and Depression Scale (HADS). Measures of psychological distress (SCL-90-R), coping style (UCL), quality of life (SF-36) and mindfulness skills (FFMQ) were administered as secondary outcome. Group effects were analyzed with repeated measures ANOVA or Friedman's test, and the individual reliability change index (RCI) was calculated per participant for each outcome measure. Semi-quantitative data included an evaluation and process measure post-intervention. Significant decline was found on the HADS-A post-intervention and after 2 months (p = 0.01), with 54% and 62% of participants demonstrating a clinically significant RCI, respectively. On the HADS-D, significant decline was found 2 months post-intervention (p = 0.04), which was driven by 23% of participants whom had a clinically significant RCI. Additional changes were found between baseline and post-intervention on the seeking distraction and reassuring thoughts subscales of the UCL, the depression and interpersonal sensitivity subscales of the SCL, the observe subscale of the FFMQ, and on physical role limitations of the SF-36 (all p < 0.05). The process evaluation form indicated that the course was found beneficial by participants, and that they applied it in a wide range of everyday situations. This exploratory pilot study indicates the feasibility of MBSR in reducing anxiety and depression in presymptomatic FTD mutation carriers and 50% at-risk individuals. A randomized controlled trial is necessary to replicate these results.

Identification of Subtle Verbal Memory Deficits in Premanifest Huntington Disease Using the California Verbal Learning Test

BACKGROUND

Verbal memory impairment in individuals with Huntington disease (HD) is well-documented; however, the nature and extent of verbal memory impairment in individuals with premanifest HD (pre-HD) are less understood.

OBJECTIVE

To evaluate verbal memory function in individuals with pre-HD by comparing their performance on the California Verbal Learning Test to that of individuals with a clinical diagnosis of HD and that of a demographically similar group of adults with no family history of, or genetic risk for, HD, thereby reducing possible complications of psychiatric difficulties commonly experienced by individuals who are at risk for HD but are gene negative.

METHODS

Participant groups included 77 adults with a diagnosis of HD, 23 premanifest gene carriers for HD (pre-HD), and 54 demographically similar, healthy adults. The California Verbal Learning Test-Second Edition (CVLT-II) was used to evaluate the participants' immediate and delayed recall, recognition, learning characteristics, errors, and memory retention.

RESULTS

The pre-HD group performed significantly worse than the healthy group, yet significantly better than the HD group, on Short and Long Delay Recall (Free and Cued) and Recognition Discriminability. On Total Immediate Recall, Learning Slope, Semantic Clustering, and Intrusions, the pre-HD group performed similarly to the healthy group and significantly better than the HD group. None of the groups differed in their performance on Repetitions and a measure of retention.

CONCLUSIONS

Subtle memory deficits can be observed during the premanifest stage of HD with use of a subset of indices from the CVLT-II.

Cognitive dysfunction in Huntington's disease: mechanisms and therapeutic strategies beyond BDNF

One of the main focuses in Huntington's disease (HD) research, as well as in most neurodegenerative diseases, is the development of new therapeutic strategies, as currently there is no treatment to delay or prevent the progression of the disease. Neuronal dysfunction and neuronal death in HD are caused by a combination of interrelated pathogenic processes that lead to motor, cognitive and psychiatric symptoms. Understanding how mutant huntingtin impacts on a plethora of cellular functions could help to identify new molecular targets. Although HD has been classically classified as a neurodegenerative disease affecting voluntary movement, lately cognitive dysfunction is receiving increased attention as it is very invalidating for patients. Thus, an ambitious goal in HD research is to find altered molecular mechanisms that contribute to cognitive decline. In this review, we have focused on those findings related to corticostriatal and hippocampal cognitive dysfunction in HD, as well as on the underlying molecular mechanisms, which constitute potential therapeutic targets. These include alterations in synaptic plasticity, transcriptional machinery and neurotrophic and neurotransmitter signaling.

Neuroimaging as a tool to study the sources of phenotypic heterogeneity in Huntington's disease

PURPOSE OF REVIEW

Huntington's disease is a neurodegenerative disorder characterized by a triad of motor, cognitive and psychiatric disturbances. There is great variability regarding the prominence and evolution of each type of clinical sign. One possible source of phenotypic heterogeneity could be the more prominent degeneration of specific brain circuits. The scope of this review is to highlight the most recent neuroimaging studies that have analysed the relationship between brain changes and motor, cognitive and psychiatric alterations in Huntington's disease.

RECENT FINDINGS

The results from recent neuroimaging studies are heterogeneous. Although there is a great overlap between the different regions associated with each symptomatic domain, there is some degree of differentiation. For example, the motor network is associated with motor impairment, whereas the ventral striatum is especially involved in emotional deficits related with psychiatric problems.

SUMMARY

Motor, cognitive and psychiatric impairments are associated with structural and functional brain biomarkers. However, the specificity of the regions involved remains unknown, because these studies focused on specific regions and symptoms. In order to tease apart the neural substrates that underlie the phenotypic heterogeneity in Huntington's disease, multivariate approaches combining brain and behavioural measures related to all symptomatic domains should be considered in the future.

A role for Kalirin-7 in corticostriatal synaptic dysfunction in Huntington's disease

Cognitive dysfunction is an early clinical hallmark of Huntington's disease (HD) preceding the appearance of motor symptoms by several years. Neuronal dysfunction and altered corticostriatal connectivity have been postulated to be fundamental to explain these early disturbances. However, no treatments to attenuate cognitive changes have been successful: the reason may rely on the idea that the temporal sequence of pathological changes is as critical as the changes per se when new therapies are in development. To this aim, it becomes critical to use HD mouse models in which cognitive impairments appear prior to motor symptoms. In this study, we demonstrate procedural memory and motor learning deficits in two different HD mice and at ages preceding motor disturbances. These impairments are associated with altered corticostriatal long-term potentiation (LTP) and specific reduction of dendritic spine density and postsynaptic density (PSD)-95 and spinophilin-positive clusters in the cortex of HD mice. As a potential mechanism, we described an early decrease of Kalirin-7 (Kal7), a guanine-nucleotide exchange factor for Rho-like small GTPases critical to maintain excitatory synapse, in the cortex of HD mice. Supporting a role for Kal7 in HD synaptic deficits, exogenous expression of Kal7 restores the reduction of excitatory synapses in HD cortical cultures. Altogether, our results suggest that cortical dysfunction precedes striatal disturbances in HD and underlie early corticostriatal LTP and cognitive defects. Moreover, we identified diminished Kal7 as a key contributor to HD cortical alterations, placing Kal7 as a molecular target for future therapies aimed to restore corticostriatal function in HD.

Assessment of motor function, sensory motor gating and recognition memory in a novel BACHD transgenic rat model for huntington disease

Rationale

Huntington disease (HD) is frequently first diagnosed by the appearance of motor symptoms; the diagnosis is subsequently confirmed by the presence of expanded CAG repeats (> 35) in the HUNTINGTIN (HTT) gene. A BACHD rat model for HD carrying the human full length mutated HTT with 97 CAG-CAA repeats has been established recently. Behavioral phenotyping of BACHD rats will help to determine the validity of this model and its potential use in preclinical drug discovery studies.

Objectives

The present study seeks to characterize the progressive emergence of motor, sensorimotor and cognitive deficits in BACHD rats.

Materials and Methods

Wild type and transgenic rats were tested from 1 till 12 months of age. Motor tests were selected to measure spontaneous locomotor activity (open field) and gait coordination. Sensorimotor gating was assessed in acoustic startle response paradigms and recognition memory was evaluated in an object recognition test.

Results

Transgenic rats showed hyperactivity at 1 month and hypoactivity starting at 4 months of age. Motor coordination imbalance in a Rotarod test was present at 2 months and gait abnormalities were seen in a Catwalk test at 12 months. Subtle sensorimotor changes were observed, whereas object recognition was unimpaired in BACHD rats up to 12 months of age.

Conclusion

The current BACHD rat model recapitulates certain symptoms from HD patients, especially the marked motor deficits. A subtle neuropsychological phenotype was found and further studies are needed to fully address the sensorimotor phenotype and the potential use of BACHD rats for drug discovery purposes.

The relationship between cortisol and verbal memory in the early stages of Huntington's disease

Hypothalamic pituitary adrenal (HPA) axis hyperactivity has been linked to learning and memory difficulties in a range of neurodegenerative and neuropsychiatric conditions. In Huntington's disease (HD), both declines in learning and memory and HPA axis dysfunction are present early in the disease. However, the relationship between specific learning and memory deficits and HPA axis functioning in HD has not been examined. The aim of this study was to investigate cortisol levels in relation to verbal learning and memory in pre-diagnosed (pre-HD) participants and patients at the early stages of diagnosed HD (early-HD). Cortisol concentration was assayed in saliva samples from 57 participants (17 early-HD, 20 pre-HD, and 20 controls) at four time-points across a 24-h period. Verbal memory was assessed using the California Verbal Learning Test-Second Edition (CVLT-II). We focused statistical analyses on the late evening cortisol concentration, and examined cortisol levels and verbal memory function in relation to diagnostic group (control, pre-HD, early-HD), and in a separate set of analyses combining pre-HD and early-HD (and excluding controls) we also examined cortisol and verbal memory performance in relation to the severity of HD-related motor signs. Of these two classification approaches, HD motor sign severity was more strongly associated with high evening cortisol levels and both reduced information encoding and memory retrieval. Separately, there was also a trend of higher cortisol levels in pre-HD. The findings suggest hypercortisolism and the underlying pathological changes may begin many years before a clinical diagnosis is made, but the memory decline associated with HPA axis disturbance may only become detectable once motor signs become pronounced.

Abnormal error-related antisaccade activation in premanifest and early manifest Huntington disease

OBJECTIVE

Individuals with the trinucleotide CAG expansion (CAG+) that causes Huntington's disease (HD) have impaired performance on antisaccade (AS) tasks that require directing gaze in the mirror opposite direction of visual targets. This study aimed to identify the neural substrates underlying altered antisaccadic performance.

METHOD

Three groups of participants were recruited: (1) Imminent and early manifest HD (early HD, n = 8); (2) premanifest (presymptomatic) CAG+ (preHD, n = 10); and (3) CAG unexpanded (CAG-) controls (n = 12). All participants completed a uniform study visit that included a neurological evaluation, neuropsychological battery, molecular testing, and functional MRI during an AS task. The blood oxygenation level dependent (BOLD) response was obtained during saccade preparation and saccade execution for both correct and incorrect responses using regression analysis.

RESULTS

Significant group differences in BOLD response were observed when comparing incorrect AS to correct AS execution. Specifically, as the percentage of incorrect AS increased, BOLD responses in the CAG- group decreased progressively in a well-documented reward detection network that includes the presupplementary motor area and dorsal anterior cingulate cortex. In contrast, AS errors in the preHD and early HD groups lacked this relationship with BOLD signal in the error detection network, and BOLD responses to AS errors were smaller in the two CAG+ groups as compared with the CAG- group.

CONCLUSIONS

These results are the first to suggest that abnormalities in an error-related response network may underlie early changes in AS eye movements in premanifest and early manifest HD. (PsycINFO Database Record (c) 2011 APA, all rights reserved).

CCG polymorphisms in the huntingtin gene have no effect on the pathogenesis of patients with Huntington's disease in mainland Chinese families

Huntington's disease (HD) is caused by the abnormal expansion of CAG repeats in the huntingtin gene (HTT). The adjacent proline-rich region, which also has a CCG polymorphism among people of different races, may also affect the pathogenesis of HD. To study the effect of this polymorphism on patients with HD in mainland China, 53 HD mutant alleles were examined. The results showed that 54.72% of the HD mutant alleles had 10-repeat alleles, and the remaining 45.28% had 7-repeat alleles. Moreover, comparison of the clinical features between the two groups revealed no significant difference. We also investigated its effect on the aggregates in vitro. No significant difference was detected when the morphology and size of the aggregates with the two polymorphisms was compared in cells. Given these findings, it was quite reasonable to suppose that the CCG polymorphism may not influence the pathogenesis of patients with HD in mainland China.

Progression in prediagnostic Huntington disease

OBJECTIVE

To examine rates of decline in individuals at risk for Huntington disease (HD).

METHODS

106 individuals at risk for HD completed a battery of neurocognitive, psychomotor and oculomotor tasks at two visits, approximately 2.5 years apart. Participants were classified as: (1) without the CAG expansion (normal controls, NC; n=68) or (2) with the CAG expansion (CAG+; n=38). The CAG+ group was further subdivided into those near to (near; n=19) or far from (far; n=19) their estimated age of onset. Longitudinal performance in the CAG+ group was evaluated with a repeated measures model with two main effects (time to onset, visit) and their interaction. Analysis of covariance was employed to detect differences in longitudinal performance in the three groups (NC, near and far).

RESULTS

In the CAG+, the interaction term was significant (p < or = 0.02) for four measures (movement time, alternate button tapping, variability of latency for a memory guided task and percentage of errors for a more complex memory guided task), suggesting the rate of decline was more rapid as subjects approached onset. Longitudinal progression in the three groups differed for several variables (p<0.05). In most, the near group had significantly faster progression than NC; however, comparisons of the NC and far groups were less consistent.

CONCLUSIONS

Different patterns of progression were observed during the prediagnostic period. For some measures, CAG+ subjects closer to estimated onset showed a more rapid decline while for other measures the CAG+ group had a constant rate of decline throughout the prediagnostic period that was more rapid than in NC.

Parallel explicit and implicit control of reaching

Background

Human movement can be guided automatically (implicit control) or attentively (explicit control). Explicit control may be engaged when learning a new movement, while implicit control enables simultaneous execution of multiple actions. Explicit and implicit control can often be assigned arbitrarily: we can simultaneously drive a car and tune the radio, seamlessly allocating implicit or explicit control to either action. This flexibility suggests that sensorimotor signals, including those that encode spatially overlapping perception and behavior, can be accurately segregated to explicit and implicit control processes.

Methodology/Principal Findings

We tested human subjects' ability to segregate sensorimotor signals to parallel control processes by requiring dual (explicit and implicit) control of the same reaching movement and testing for interference between these processes. Healthy control subjects were able to engage dual explicit and implicit motor control without degradation of performance compared to explicit or implicit control alone. We then asked whether segregation of explicit and implicit motor control can be selectively disrupted by studying dual-control performance in subjects with no clinically manifest neurologic deficits in the presymptomatic stage of Huntington's disease (HD). These subjects performed successfully under either explicit or implicit control alone, but were impaired in the dual-control condition.

Conclusion/Significance

The human nervous system can exert dual control on a single action, and is therefore able to accurately segregate sensorimotor signals to explicit and implicit control. The impairment observed in the presymptomatic stage of HD points to a possible crucial contribution of the striatum to the segregation of sensorimotor signals to multiple control processes.

Temporal order memory deficits prior to clinical diagnosis in Huntington's disease

The current study examined temporal order memory in preclinical Huntington's disease (pre-HD). Participants were separated into less than 5 years (pre-HD near) and more than 5 years (pre-HD far) from estimated age of clinical diagnosis. Participants completed a temporal order memory task on a computerized radial eight-arm maze. On the study phase of each trial, participants viewed a random sequence of circles appearing one at a time at the end of each arm. On the choice phase, participants viewed two circles at the end of the study phase arms and chose the circle occurring earliest in the sequence. The task involved manipulations of the temporal lag, defined as the number of arms occurring in the sample phase sequence between the two choice phase arms. Research suggests that there is more interference for temporally proximal stimuli relative to temporally distal stimuli. There were no significant differences between the pre-HD far group and controls on the temporal order memory task. The pre-HD near group demonstrated significant impairments relative to the other groups on closer temporal lags, but were normal on the furthest temporal lag. Therefore, temporal order memory declines with increased temporal interference in pre-HD close to estimated diagnosis of HD.

Neuropsychological deficits in Huntington's disease gene carriers and correlates of early "conversion"

The authors examined whether the baseline cognitive functioning of 21 clinically normal huntingtin mutation carriers who developed manifest Huntington's disease on follow-up differed from that of 49 mutation carriers who remain asymptomatic over the same period in a longitudinal study. One hundred thirty-four gene-negative offspring of Huntington's disease patients were studied as well. Overall, there were no differences in cognitive test performance among the three groups. However, "converters" who developed signs of Huntington's disease within 8.6 years demonstrated poorer performance on the Wisconsin Card Sorting Test at baseline. People with the Huntington's disease mutation who are carefully examined neurologically and found to be asymptomatic have, at most, very minimal problem-solving impairment, and only if they are within a few years of clinical onset.

Higher levels of extroverted hostility detected in gene carriers at risk for Huntington's disease

BACKGROUND

Numerous retrospective studies have reported the presence of psychiatric disorders at the prodromal or early stages of Huntington's disease (HD). However, most of the studies comparing gene carriers with non-carriers before the clinical manifestation of the illness have failed to reveal differences in the psychiatric manifestation. The objective of the present study was to detect behavioral and psychological features that differentiate gene carriers from non-carriers.

METHODS

Eighty-one Greek patients at 50% risk for HD were recruited prospectively and examined by means of a semi-structured interview and four self-rated questionnaires. The study focused predominantly on hostility/irritability and obsessional behavior.

RESULTS

Gene carriers had significantly higher extroverted hostility than non-carriers (p = .005). The elevated level of hostility was unaffected by the proximity to the estimated age of onset. The remainder of the scales did not reveal significant differences.

CONCLUSIONS

Extroverted hostility, in particular criticism of others and delusional hostility, is increased in gene carriers well before the onset of clinical HD. Hostility is regarded as a personality dimension rather than as a behavioral pattern.

Cognitive changes in asymptomatic carriers of the Huntington disease mutation gene

Huntington disease (HD) is a neurodegenerative disorder due to an excessive number of CAG repeats in the IT15 gene on chromosome 4. Studies of cognitive function in asymptomatic gene carriers have yielded contradictory results. This study compared cognitive performance in 44 subjects with the HD mutation (group of carriers) who had no clinical signs of HD and 39 at-risk individuals without HD mutation (group of non-carriers). Neuropsychological evaluation focused on global cognitive efficiency, psychomotor speed, attentional, executive and memory functions. Significant differences, with lower performances in the group of gene carriers, were detected for some measures of psychomotor speed, attention and executive functioning (all P < 0.01). More differences between groups were observed for memory measures, in particular on the California Verbal Memory Test. Complementing these observations, cognitive scores were correlated with age in the group of gene carriers, but not in the group of non-carriers. This suggests that the cognitive changes precede the appearance of the motor and psychiatric symptoms in HD and that tests proved to be sensitive to early HD deficiencies are better suited than global cognitive efficiency scales to observe them.

"No one else sees the difference: "family members' perceptions of changes in persons with preclinical Huntington disease

Manifestations of Huntington disease (HD) prior to clinical diagnosis are not well understood. This study documents adult family members' perceptions of changes and their attempts to manage these changes in persons who had received a positive predictive molecular HD test prior to clinical diagnosis. Data were obtained from 19 adult family members in six focus groups in the US and Canada and one individual interview in the US. Changes reported by family members included problems in cognition and behavior, which are consistent with prior reports. In addition, family members observed changes in motor functioning, the ability to complete usual activities at work or at home, and interpersonal relationships with family and friends. Family members attempted to manage these changes by taking on new responsibilities and preparing for future caregiving. Lack of information about preclinical HD, difficulty in understanding changes that may represent early stages of HD, and efforts to maintain secrecy of the preclinical HD situation contribute to compromising the abilities of family members to respond to changes in the person with preclinical HD. Findings provide insights into alterations in cognition, behavior, and functioning observed by the family members prior to clinical diagnosis. Findings further support the need for a more comprehensive assessment and management of early HD symptoms as well as support for family members.

Attention, inhibition, and proximity to clinical onset in preclinical mutation carriers for Huntington's disease

Research in preclinical mutation carriers for Huntington's disease (HD) aims to find measures sensitive to preclinical decline. This study investigated attentional abilities in mutation carriers and noncarriers. Mutation carriers demonstrated a normal "attentional blink" during rapid serial visual presentation, normal covert visual orienting, and normal directing of attention to tactile stimuli. However, they were more likely than noncarriers to make anticipatory responses before target presentation. Additionally, those closer to estimated onset of HD demonstrated larger "inhibition of return" effects. The findings suggest potential changes in cognitive inhibition of unwanted responses, and in automatic inhibition of visual orienting, in preclinical HD.

Proximity to clinical onset influences motor and cognitive performance in presymptomatic Huntington disease gene carriers

BACKGROUND

Neuroimaging studies of Huntington disease (HD) gene carriers have shown that characteristic striatal atrophy begins long before symptom onset, but findings regarding the presence of preclinical functional deficits are inconsistent.

OBJECTIVE

To further investigate potential motor and cognitive deficits in presymptomatic gene carriers (PSGCs), and relationships between performance and estimated proximity to HD symptom onset.

METHOD

PSGCs and age-matched controls performed motor tasks involving cued sequential button presses, and cognitive tasks involving simple and complex choice responses to visuospatial stimuli.

RESULTS

PSGCs demonstrated similar motor performance speed, and nonsignificantly slower cognitive reaction times, to controls. PSGCs made more errors than controls to stimuli requiring a spatially incongruent response, possibly suggesting some difficulty in inhibiting automatic responses. Movement times for motor conditions where little advance information was provided, and reaction times for low demand cognitive tasks, were positively correlated with PSGCs' estimated probability of symptom onset within 5 years.

CONCLUSIONS

Response speed was slower for those PSGCs estimated to have higher probabilities of close onset. These findings suggest that to provide improved knowledge of how HD begins, knowledge that may be used in clinical trials, future research should further explore relationships between function and proximity to onset.

Verbal episodic memory declines prior to diagnosis in Huntington's disease

Previous studies of verbal episodic memory in pre-diagnostic Huntington's disease (HD) have yielded mixed results; some evidence suggests that memory decline is evident prior to the onset of pronounced neurological signs of HD, whereas other data indicate that memory function remains normal throughout the pre-diagnostic period. This study examines verbal episodic memory in a sample of CAG expanded individuals who have not yet been clinically diagnosed, and who represent a wide range of points along the continuum from health to disease. The Hopkins Verbal Learning Test-Revised (HVLT-R) was administered to 479 participants (428 with the HD CAG expansion and 51 without), and performance was compared to neurobiological indices of disease progression, including a DNA-based estimate of proximity to clinical diagnosis, magnetic resonance imaging (MRI) measures of striatal volume, and neurologist ratings of motor signs. Lower HVLT-R scores were associated with closer proximity to clinical diagnosis and smaller striatal volumes; these relationships were found even in groups with no neurological signs of HD. The CAG expanded groups, including those with only minimal neurological signs, had significantly lower HVLT-R scores than the control group, and performance was worse in sub-groups that had more neurological signs consistent with HD. These findings indicate that verbal episodic memory is affected in early pre-diagnostic HD and may decline as striatal volumes decrease and individuals approach the motor diagnostic threshold.

Episodic memory impairment in Huntington's disease: a meta-analysis

Memory dysfunction is an important feature in the clinical presentation of Huntington's disease (HD) and may precede the onset of motor symptoms. Although several studies have contributed to the quantitative and qualitative description of memory impairments in HD, the characterization of episodic memory impairments has varied considerably. Whereas most studies report significant impairments on free recall tests, performance on recognition tests has been considerably more variable, ranging from normal to markedly deficient. This absence of a well-established recognition memory deficit has led some investigators to attribute the memory deficits in HD to a retrieval-based episodic memory impairment. We felt that a quantitative review of the literature was needed to better characterize these episodic memory impairments. We conducted a meta-analysis to assess the magnitude of the recognition memory deficit in HD and to examine it in relation to the known deficit in recall. Memory data were provided by 544 symptomatic HD patients, 224 presymptomatic gene-carriers, and 963 control subjects. The overall group comparison between symptomatic patients and controls yielded effect sizes of d=1.95 for free recall and d=1.73 for recognition. We split the symptomatic group into two subgroups based on their mental status (mild and moderate/severe dementia) and both showed significant deficits in recall and recognition memory, though recall was more impaired than recognition in the mild dementia subgroup. Only slight memory impairment was observed in the presymptomatic subjects. The results show that deficits in recognition memory must be accounted for in future models of memory impairment in HD.

Early development of aberrant synaptic plasticity in a mouse model of Huntington's disease

Huntington's disease (HD) is a fatal neurodegenerative disorder characterized by progressive motor, psychiatric and cognitive decline. Marked neuronal loss occurs in the cortex and striatum. HD is inherited in an autosomal dominant fashion and caused by a trinucleotide repeat expansion (CAG) in the gene encoding the protein huntingtin. Predictive genetic testing has revealed early cognitive deficits in asymptomatic gene carriers at a time when there is little evidence for cell death, suggesting that impaired cognition results from a cellular or synaptic deficit, such as aberrant synaptic plasticity. Altered hippocampal long-term potentiation has been reported in mouse models of HD; however, the relationship between synaptic dysfunction and phenotype progression has not previously been characterized. We examined the age-dependency of aberrant hippocampal synaptic plasticity in the R6/1 mouse model of HD. Long-term depression (LTD) is a developmentally regulated form of plasticity, which normally declines by early adulthood. Young R6/1 mice follow the same pattern of LTD expression as controls, in that they express LTD in the first weeks of life, and then lose the ability with age. Unlike controls, R6/1 synapses later regain the ability to support LTD. This is associated with nuclear localization of mutant huntingtin, but occurs months prior to the formation of nuclear aggregates. We present the first detailed description of a progressive derailment of a functional neural correlate of cognitive processing in HD.

Presymptomatic signs in healthy CJD mutation carriers

Creutzfeldt-Jacob disease (CJD) is a rapidly progressing dementia with neurological, psychiatric and cognitive symptoms. We focused our study on the familial CJD form among Libyan Jews (the E200K mutation), trying to identify preclinical neuropsychological signs in mutation carriers to facilitate early diagnosis of the disease. A wide range of neuropsychological tests was administered to 27 healthy volunteers, all first-degree relatives of genetic CJD patients. Thirteen of our participants were gene mutation carriers (E200K) and 14 controls. The healthy mutation carriers reported significantly lower Trait and higher State anxiety scores. Repeated Measure analysis showed statistical significance. The Anxiety Index (State-Trait Anxiety Score) progressed with age in the carriers' group but not in the controls. Since this was more pronounced in the older subjects, we suggest that abnormal stress mechanisms precede the clinical onset of CJD. Cognitive differences have also been found between carriers and controls, especially in visual recognition of pictured objects. Both kinds of differences (anxiety levels and cognitive deficits) were most pronounced in elderly subjects. This study is the first to show any dysfunction in healthy CJD mutation carriers.

Cognitive changes in patients with Huntington's disease (HD) and asymptomatic carriers of the HD mutation--a longitudinal follow-up study

OBJECTIVE

Objective information about the onset and progression of cognitive impairment in Huntington's disease (HD) is very important in the light of appropriate outcome measures when conducting clinical trials. Therefore, we evaluated the progression of cognitive functions in HD patients and asymptomatic carriers of the HD mutation (AC) over a 2.5-year period. We also sought to detect the earliest markers of cognitive impairment in AC.

METHODS

A prospective study comparing HD patients, clinically asymptomatic HD mutation-carriers (AC) and non-carriers (NC). These groups were examined three times during a period of 2.5 years. At baseline the study sample consisted of 49 subjects. Forty-two subjects (19 HD patients, 12 AC and 11 NC) completed three assessments. A battery of neuropsychological tests measuring intelligence, attention, memory, language, visuospatial perception, and executive functions was performed.

RESULTS

The performance of HD patients deteriorated on the following cognitive tests: Symbol Digit Modalities Test (SDMT), Stroop Colour and Word, Boston Naming Test (BNT), Object and Space Perception and Trail Making Test-B. Longitudinal comparison of AC and NC revealed that performances on SDMT, Block Span, Digit Span Backwards, Hopkins Verbal Learning Test (learning and delayed recall) and Conditional Associative Learning Test are impaired in AC.

CONCLUSIONS

Tasks measuring mainly attention, object and space perception and executive functions adequately assess the progression of HD disease. Other cognitive functions do not significantly deteriorate. Furthermore, problems in attention, working memory, verbal learning, verbal long-term memory and learning of random associations are the earliest cognitive manifestations in AC.

Arrangement de scripts dans la maladie de Huntington

According to Norman and Shallice, the basal ganglia are involved in the activation and maintenance of overlearned or routine scripts in action planning. This study aimed to investigate how patients with Huntington disease manipulate scripts. Ten patients with Huntington's disease and 12 normal control subjects matched by age and education were asked to re-establish the sequential order of series of script actions which were given with or without distractor elements (i.e. with or without actions belonging to trivial scripts). Compared with normal controls, patients with Huntington disease made significantly more errors in script sequencing. However there was no significant difference in performance between patients with Huntington disease and normal control subjects in inhibiting irrelevant actions. These results suggest that early Huntington's disease patients exhibit early impairment in their ability to produce temporally coherent sequences without deficit in their ability to eliminate distractors in the action domain. These results support in part the predictions of Norman and Shallice's model. From a neuroanatomical point of view, this dissociation of performance fits with what is known about the neuropathological progression of Huntington's disease in which neuronal loss progresses in a dorsal-to-ventral direction and with what was shown in patients with circumscribed frontal lobe damage. In these patients, impairment in script sequencing is related to lesions in the lateral prefrontal regions.

Visual function in Huntington's disease patients and presymptomatic gene carriers

Disturbances of visual cognition, visuomotor performance, and visual memory have been described frequently in Huntington's disease (HD). Early stage visual abnormalities could contribute to these deficits. We evaluated visual processing in 20 control subjects who were non-gene carriers at risk for HD, nine presymptomatic gene-positive subjects, and eight subjects with a recent diagnosis of Huntington's disease. Visual perceptual tests of contrast sensitivity and motion discrimination were used to probe early stage visual processing. Extraocular movements were evaluated in a neurologic examination, and the Digit Symbol test was used to test visual motor performance. Contrast sensitivity did not differ among the three groups. Motion discrimination was impaired in HD subjects but not in the presymptomatic gene carriers when compared to gene noncarriers. Among gene carriers, impaired motion discrimination performance was associated with poorer Digit Symbol performance and extraocular abnormalities. These findings suggest that the early stages of HD are associated with disturbances of motion perception as well as disruptions of visual motor and ocular motor performance.

Future directions in research with presymptomatic individuals carrying the gene for Huntington's disease

Presymptomatic individuals carrying the gene for Huntington's disease (HD) provide researchers with a unique opportunity of learning more about the neuropathophysiology, symptom onset, behavioural functioning, and mediating factors of this fatal disease. In this review, we attempt to demonstrate that research over the last 8 years, since the isolation of the gene, has remained at large controversial. Although we are aware of some of the factors that can influence age at onset and disease progression, we are still unable to determine exactly when an individual will develop HD symptoms, and how fast these symptoms will progress. In an era rapidly advancing with respect to therapeutic intervention that could forestall the onset and progression of HD, systematic research with improved inclusion criteria is paramount. A greater understanding of the time course of the disease would be beneficial not only in monitoring the effectiveness of future treatments, but also in determining the most appropriate time to administer them. Finally, we present various ethical considerations, as well as put forward various recommendations that could assist in better diagnosing preclinical deficits in presymptomatic individuals.

Predictive Testing for Huntington's Disease: How Does it Impact on Cognitive Performance?

The discovery of a polymorphic DNA marker for Huntington's Disease (HD) in 1983, and the specific gene responsible in 1993, led to predictive testing programmes out of which came research into whether or not cognitive impairment was present presymptomatically in those at risk for HD. The results of these studies have been conflicting and inconclusive. Methodoiogical limitations have probably contributed to the differing findings. The present study attempted to expand upon previous studies by analysing the data in a more comprehensive manner, and with additional control conditions. In this study, 26 individuals, at risk but presymptomatic, for HD were recruited from the Johannesburg Predictive Testing Programme and administered a battery of psychological tests prior to molecular analysis. Of this HD group, 11 were subsequently positive for the gene (the HD+ group) and 15 were negative (HD- group). A carefully chosen control group, (matched for age, sex, and education - Control Group 1) and a group of individuals experiencing a life threatening medical illness (without CNS involvement - Control Group 2) were administered the same battery of psychological tests. Four-way Analysis of Variance between the HD+, HD-, and Control groups was conducted to detect specific differences between the groups. The results indicated that the HD+ group showed mild impairment for declarative memory function. However, it would appear that undergoing the psychological evaluation itself impacted upon the test performance of both the HD+ and HD- groups.

Subjective emotional experience and cognitive impairment in drug-induced akathisia

The purpose of this study was to characterize the subjectively experienced symptoms and cognitive impairment associated with akathisia, which is among the most disabling adverse effects associated with antipsychotic drugs. While subjective experience is considered to be an integral part of akathisia, only a few studies have comprehensively investigated the specific contents of the subjective experiences or of the discomforts of patients with drug-induced akathisia. In addition, the precise relationship of akathisia to cognitive impairment, one of the main constituents of subjective experiences, is largely unknown. Forty-one stable and chronic schizophrenic patients, who were receiving maintenance antipsychotic treatment, were rated using the Barnes Akathisia Rating Scale (BARS) for drug-induced akathisia. Subjective experiences were evaluated using the Symptom Checklist-90-Revised (SCL-90-R), and cognitive function was assessed using the Wechsler Memory Scale (WMS). Analysis of covariance (ANCOVA) with relevant variables as covariates revealed that patients with akathisia (n = 17) had significantly higher scores on the depression subscale of the SCL-90-R than those without akathisia (n = 24). Patients with akathisia also had significantly lower scores on the mental control subtest of the WMS. Further analysis using ordinal logistic regression revealed that the depression subscale of SCL-90-R and the mental control subtest of WMS were significantly associated with the severity of akathisia. These results suggest that akathisia is significantly associated with depressive symptoms and attentional impairment, which reflects the complex nature of akathisia that includes motor, emotional, and cognitive aspects. Several methodological considerations and future directions are discussed.

Longitudinal study evaluating neuropsychological changes in so-called asymptomatic carriers of the Huntington's disease mutation after 1 year

OBJECTIVES

To determine (1) whether the battery of neuropsychological tests was sufficiently sensitive to find differences between symptomatic patients with Huntington's disease (HD) and clinically asymptomatic individuals carrying the HD gene (AGC) and individuals without the HD gene (NGC) and (2) whether increasing cognitive impairment is found in AGC as compared with NGC.

METHODS

A case-control, single-blind study comparing subjects with clinically manifest HD (n=21), AGC (n=12) or NGC (n=11) and a 1-year follow-up of AGC and NGC. Genotype for the HD gene was determined by molecular testing. A large battery of neuropsychological tests measuring several cognitive domains was performed.

RESULTS

On most neuropsychological tasks, HD patients perform significantly worse than AGC and NGC. At baseline and follow-up examination, compared with NGC, AGC had lower scores on the symbol digit modalities test. Scores on a block span task declined more rapidly among AGC than among NGC.

CONCLUSION

Cognitive impairments in HD patients are found when compared with clinically asymptomatic individuals carrying the HD mutation. Furthermore, our results suggest that subtle cognitive deficits are present in asymptomatic persons who have inherited the HD gene.

Psychological features in persons at risk for familial Alzheimer's disease

Persons at risk for inherited neurodegenerative diseases may experience symptoms of anxiety and depression because of concern over the possibility of developing the disease in the future. The purpose of this study was to assess psychological and emotional symptoms in persons at the age of risk for developing early-onset familial Alzheimer's disease (FAD). Their responses on a psychiatric rating scale (SCL-90-R) were compared with four groups: patients with mild FAD; head injury patients; patients with clinically diagnosed depression; and healthy control subjects. Mean scores of the at-risk FAD group were not statistically different than those of the controls. In contrast, the head injury and depressed groups had significantly elevated scores across the clinical scales. These results suggest that depression and anxiety are not prominent features in persons at genetic risk for early-onset familial Alzheimer's disease. Similar results have been found in studies of persons at risk for developing Huntington's disease, another autosomal dominant neurodegenerative disease.

Subtle changes among presymptomatic carriers of the Huntington's disease gene

OBJECTIVES

To compare the neurological and psychometric characteristics of presymptomatic gene carriers and non-gene carriers who are at risk for developing Huntington's disease so as to characterise early signs of disease and to identify markers of neurological function that could be used to assess the impact of experimental therapies on the progression of disease, even among those who are clinically presymptomatic.

METHODS

A sample of people at risk for Huntington's disease was genotyped and evaluated using subscales of the Wechsler adult intelligence scale-revised (WAIS-R), a quantified neurological rating scale, and computerised physiological measures including speed of movement and reaction time.

RESULTS

Genotyping and clinical examination determined that 171 participants were presymptomatic gene carriers (PSGCs) and 414 participants were non-gene carriers (NGCs). The PSGCs performed significantly worse when compared with the NGCs on the digit symbol, picture arrangement, and arithmetic subscales of the WAIS-R (p<0.02) and for the physiological measures: button tapping, auditory reaction time, visual reaction time with decision, and movement time with and without decision (p<0.05). Although no PSGCs had sufficient neurological findings to warrant a diagnosis of Huntington's disease on clinical examination, the PSGCs had more frequent possible or definite abnormality for oculomotor function, chorea, muscle stretch reflexes, gait, and station stability, and rapid alternating movements (p</=0.02).

CONCLUSIONS

Among Huntington's disease gene carriers, subtle cognitive and motor deficits precede the onset of sufficient neurological abnormality to warrant a clinical diagnosis of Huntington's disease.

Psychopathological changes preceding motor symptoms in Huntington's disease: a report on four cases

Neurodegenerative disorders often exhibit "classical" psychiatric symptoms as an initial presentation of the disease. Here we present four patients with different psychopathological abnormalities who were later diagnosed as having Huntington's disease. The range of symptoms covered affective and psychotic symptoms, antisocial behavior, cognitive problems reminiscent of dementia and suicidal idealisation. The pattern of progress of neuronal degeneration may be helpful in explaining the antecedent manifestation of psychiatric symptoms.

Huntington's disease: neurological assessment of potential gene carriers presenting for predictive DNA testing

One hundred and fifty-six potential gene carriers who were 50% 'at risk' of inheriting the Huntington's disease (HD) mutation, and who presented for predictive testing, underwent neurological assessment before their gene status had been determined. The association between pre-gene result symptoms and minimal neurological signs (insufficient for diagnosis in their own right) and subsequent gene status was determined. Of these, 38% tested positive for the HD mutation. Fifty-one individuals had minor neurological signs. After exclusions, 61% of gene-positive patients had minor neurological signs, whereas only 8% testing gene negative had signs. Minimal chorea observed in the toes and feet with the subject supine, and the patient being stressed by a mental task carried 96% specificity and 86% positive predictive value for gene-positive status. Neurological symptoms did not distinguish gene status, but behavioural and cognitive symptoms were more often reported by the gene-positive group. Although an 'at-risk' individual may receive a gene-positive result, neurological examination remains the most accessible, reliable and cost effective means of determining clinical disease onset.

Subtle involuntary movements are not reliable indicators of incipient Huntington's disease

In the past, Huntington's disease was diagnosed when movement disturbances were present in concordance with a positive family history. Early motor signs, however, are often not found in a standard neurologic examination, and their expression is variable. Not until later stages of the disease could one be sure about the diagnosis. Since genetic diagnosis became available, the onset of symptoms and signs could be studied in the earliest phase. The aim of the study was to evaluate observer agreement of the assessment of early motor signs in Huntington's disease. A total of 17 gene carriers, 22 noncarriers, and eight partners were recorded on video performing several facial movements after instruction and engaging in a 5-minute conversation. Three experienced neurologists, unaware of the genetic status of the participants, judged and classified the video recordings independently. The cases with disagreement were judged a second time after the neurologists discussed these cases. The observer agreement after the first judgment is poor (kappas 0.09, 0.24, 0.45) and after the second judgment satisfactory (kappas 0.79, 0.90, 0.78). Consequences for clinical practice and research programs into early symptoms and signs are discussed.

Intelligence indices in people with a high/low risk for developing Huntington's disease

Intelligence in 20 presymptomatic subjects with an increased risk (> 95%) for carrying the gene for Huntington's disease (HD) was studied in a prospective, case-control, single blind study. No significant differences between the groups were detected for intelligence indices and subtest scores (Wechsler Adult Intelligence Scale). The high level of the performance IQ and the significant discrepancy between performance IQ and verbal IQ found in both the high risk and the low risk groups contrasted with our expectations based on anamnestic information, general clinical opinion, and the results of previously conducted studies. We propose that psychosocial circumstances could explain the test results and discuss the consequences of our findings for clinical genetics practice.